Method and apparatus for inducing strain into optical devices

Abstract

An optical device including strained and non-strained regions along an optical medium. In one aspect of the present invention, strain-inducing material disposed proximate to the optical medium induces one or more perturbations of a refractive index along the optical medium to selectively reflect an optical beam directed through the optical medium having a first center wavelength back out a first end of an optical path as remaining wavelengths of light are propagated through a second end. In another embodiment, an optical device may include a strained region disposed in a non-strained region so that one or more perturbations of the refractive index compensates for birefringence of an optical beam directed through the optical medium.

1. An apparatus, comprising:
 a plurality of strained and non-strained regions along an optical medium including one or more perturbations of a refractive index along the optical medium to selectively reflect a first center wavelength of an optical beam directed through the optical medium back out a first end of an optical path, remaining wavelengths of the optical beam to propagate through a second end of the optical path; and  
 strain-inducing material disposed proximate to the optical medium.  
 
   
   
     2. The apparatus of  claim 1  wherein the optical medium includes a semiconductor material. 
   
   
     3. The apparatus of  claim 2  wherein the semiconductor material includes at least one of silicon, gallium arsenide, indium phosphide and lithium niobate. 
   
   
     4. The apparatus of  claim 1  wherein the optical medium includes at least one of silica or glass. 
   
   
     5. The apparatus of  claim 1  wherein the one or more perturbations of a refractive index are induced by the strain-inducing material disposed proximate to the optical medium. 
   
   
     6. The apparatus of  claim 1  wherein the strain-inducing material includes at least one of silicon nitride (Si3N4) or silicon dioxide (SiO2). 
   
   
     7. The apparatus of  claim 1  further comprising an optical waveguide disposed in the optical medium, the optical waveguide including the optical path. 
   
   
     8. The apparatus of  claim 1  wherein the plurality of strained and non-strained regions including one or more perturbations of the refractive index along the optical medium provide a Bragg grating disposed in the optical medium. 
   
   
     9. The apparatus of  claim 1  wherein the strain-inducing material disposed proximate to the optical medium has a pitch having a width of the strain-inducing material and an adjacent exposed area of the optical medium. 
   
   
     10. A method, comprising:
 directing an optical beam into a first end of an optical path having the first end and a second end disposed in an optical medium, the optical path having a plurality of periodic strain-induced perturbations of a refractive index of the optical medium along the optical path; and  
 reflecting a first portion of the optical beam having a first center wavelength back out from the first end of the optical path.  
 
   
   
     11. The method of  claim 10  wherein reflecting the first portion of the optical beam includes controlling the refractive index by controlling an amount of strain along the plurality of periodic strain-induced perturbations. 
   
   
     12. The method of  claim 11  wherein controlling the amount of strain includes varying a thickness of a layer of a region of strain-inducing material disposed proximate to the optical medium. 
   
   
     13. An apparatus, comprising:
 a strained region disposed in a non-strained region along an optical medium including a strain-induced perturbation of a refractive index along the optical medium to compensate for birefringence of an optical beam directed through the optical medium;  
 strain-inducing material disposed proximate to the optical medium;  
 an insulating layer disposed proximate to the optical medium such that the optical medium is disposed between the strain inducing material and the insulating layer; and  
 a substrate layer disposed proximate to the insulating layer such that the insulating layer is disposed between the optical medium and the substrate layer.  
 
   
   
     14. The apparatus of  claim 13  wherein the optical medium includes a semiconductor material. 
   
   
     15. The apparatus of  claim 14  wherein the optical medium is included in a silicon-on-insulator (SOI) wafer, wherein the insulating layer is the insulator of the SOI wafer. 
   
   
     16. The apparatus of  claim 13  wherein the strain-induced perturbation is induced by the strain-inducing material disposed proximate to the optical medium. 
   
   
     17. The apparatus of  claim 13  wherein the strain induced perturbation of the refractive index provides a refractive index difference to a portion of the optical beam having one of a plurality of polarizations to compensate for birefringence. 
   
   
     18. A method, comprising:
 directing an optical beam into a first end of an optical path having the first end and a second end disposed in an optical medium, the optical medium included in an optical waveguide defined in a semiconductor layer of a silicon-on-insulator (SOI) wafer including an insulating layer and a substrate layer, the substrate layer disposed proximate to the insulating layer such that the insulating layer is disposed between the optical medium and the substrate layer; and  
 compensating for birefringence of the optical beam by directing a portion of the optical beam having one of a plurality of polarizations through a strain-induced perturbation of a refractive index of the optical medium along the optical path, the optical medium disposed between the insulating layer and strain-inducing material disposed proximate to the optical medium.  
 
   
   
     19. The method of  claim 18  wherein compensating for birefringence includes controlling the refractive index of the optical medium to control an amount of strain at the strain-induced perturbation. 
   
   
     20. The method of  claim 19  wherein controlling the amount of strain at the strain-induced perturbation includes varying a thickness of the strain-inducing material disposed proximate to the optical medium. 
   
   
     21. A method, comprising:
 patterning a mask on a silicon-on-insulator (SOI) wafer including a strain-inducing layer disposed over a semiconductor layer of the SOI wafer, the SOI wafer further including an insulating layer and a substrate layer, the insulating layer disposed between the semiconductor layer and the substrate layer, the semiconductor layer disposed between the strain-inducing layer and the insulating layer;  
 etching the strain-inducing layer to define periodic strained regions in the semiconductor layer of the SOI wafer; and  
 etching a waveguide in the semiconductor layer of the SOI wafer.  
 
   
   
     22. The method of  claim 21  wherein patterning the mask comprises patterning a photoresist layer to form the mask. 
   
   
     23. The method of  claim 21  wherein etching includes at least one of a wet etch and a dry etch. 
   
   
     24. A method, comprising:
 patterning a mask on a silicon-on-insulator (SOI) wafer including a strain-inducing layer disposed over a semiconductor layer of the SOI wafer, the SOI wafer further including an insulating layer and a substrate layer, the insulating layer disposed between the semiconductor layer and the substrate layer, the semiconductor layer disposed between the strain-inducing layer and the insulating layer;  
 etching the strain-inducing layer to define a strained region in the semiconductor layer of the SOI wafer to compensate for birefringence; and  
 etching a waveguide in the semiconductor layer of the SOI wafer.  
 
   
   
     25. The method of  claim 24  wherein patterning the mask comprises patterning a photoresist layer to form the mask. 
   
   
     26. The method of  claim 24  wherein etching includes at least one of a wet etch and a dry etch. 
   
   
     27. A system, comprising:
 an optical transmitter to transmit an optical beam;  
 an optical receiver optically coupled to the optical transmitter to receive the optical beam; and  
 an optical device including an optical medium defined in a semiconductor layer of a silicon-on-insulator (SOI) wafer and coupled between the optical transmitter and the optical receiver, the optical device to include a plurality of periodic strain-induced perturbations of a refractive index of the optical medium along an optical path, the SOI wafer including an insulating layer and a substrate layer, the insulating layer disposed between the semiconductor layer an the substrate layer, the semiconductor layer disposed between a strain-inducing layer disposed over the semiconductor layer and the insulating layer.  
 
   
   
     28. The system of  claim 27  wherein the optical device includes a Bragg grating. 
   
   
     29. The system of  claim 27  wherein the plurality of periodic strain-induced perturbations are induced by strain-inducing material disposed proximate to the optical medium.